JPS6311433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing electrolytic corrosion of a magnesium alloy member at a portion where bolts are assembled with a high tightening force and in the vicinity thereof.

Magnesium alloys are expected to be a substitute for aluminum-based metal materials in the automobile industry and the like. However, magnesium alloys have the disadvantage of being susceptible to contact corrosion when brought into contact with zinc. Therefore, magnesium alloy parts that were conventionally assembled with bolts using galvanized washers,
When exposed to moisture or other corrosive environments, severe electrolytic corrosion occurs around the washer of the alloy member, resulting in poor appearance and, if severe, problems such as bolt loosening, etc., occur.

In order to deal with this problem of electrolytic corrosion, methods such as painting the metal to give it insulation properties have been used, but with these methods, the paint film is often scratched when bolts are tightened, resulting in significant damage. In some cases, the coating film is destroyed and the metals come into contact with each other, which causes a problem in that the insulation effect is impaired.

The present invention solves the above problems and provides a method for preventing electrolytic corrosion in and around areas of magnesium alloy members where bolts are assembled with high tightening force much better than in the past. .

In the method of the present invention, when bolting a magnesium alloy member using a galvanized washer with a high tightening force, a washer made of an insulating material ( By assembling an insulating washer (hereinafter referred to as an insulating washer) so that the surrounding area of the galvanized washer does not come into direct contact with the magnesium alloy member, the galvanized washer and the magnesium alloy member are electrically contacted under corrosive conditions. It is characterized in that it prevents

The galvanized washer is used to obtain the effect of a conventional washer, and the conventional washer can be used as is, or if necessary, it may be used with appropriate modification.

As the material of the insulating washer, any insulating material with excellent durability and strength can be used. For example, ceramic is suitable because it has excellent strength and there is no problem of the axial force of the bolt being reduced due to wear and tear, but plastic materials such as silicone rubber can also be used.

In order to ensure sufficient insulation between the galvanized washer and the magnesium alloy member, the thickness of the insulating washer should be 2 mm or more, and its diameter should be approximately 2 mm larger than the diameter of the galvanized washer. It is preferable. That is, with such a structure, even if a small amount of electrolyte, such as moisture or acid, adheres to the outer periphery of the insulating washer, electrolytic corrosion will not occur at all. In addition, even if electrolyte accumulates and the galvanized washer and magnesium alloy member are electrically connected, the distance between them is greater and the resistance is greater, so the occurrence of electrolytic corrosion must be kept to a minimum. Can be done.

Next, the present invention will be explained in more detail based on the drawings.

FIG. 1 is a diagram showing an embodiment of the method of the present invention. A ceramic insulating washer 3 having a diameter larger than that of the washer 2 and having a thickness of 2 mm is sandwiched between the galvanized washer 2 and the magnesium alloy member 4, and the magnesium alloy member 4 is assembled to the mating member with the bolt 1. Ta.

FIG. 2 is a diagram showing another embodiment of the method of the present invention. The outer periphery of the galvanized washer 2 has a stepped structure, and the width between the step and the magnesium alloy member is approximately 2.
An insulating washer 3 made of an insulating sealing material such as silicone rubber was sandwiched in a gap of 1 mm, and the magnesium alloy member was assembled to the mating member. The thickness of this insulating washer 3 is made slightly thicker than the width of the stepped portion so that the washer 3 is compressed and a sealing effect is obtained when the bolt is tightened. In this case, the diameter of insulating washer 3 is also 2 mm larger than the diameter of galvanized washer 2.
I made it bigger.

Even if electrolyte 5 accumulates outside the washer 3 at the assembly location shown in FIGS. 1 and 2 above, the end of the galvanized washer and the surface of the magnesium alloy member are sufficiently far apart, so electrolytic corrosion of the magnesium alloy occurs. almost never occurred.

As explained above, the present invention solves the problem of electrolytic corrosion in and around the parts of magnesium alloy members where bolts are assembled with high tightening force.
This significantly expands the scope of application of magnesium alloy members as automobile parts.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the method of the present invention, and FIG. 2 is a diagram showing another embodiment of the method of the present invention. 1... Bolt, 2... Galvanized washer, 3
...Insulating washer, 4...Magnesium alloy member, 5...Electrolyte.

Claims (1)

[Claims] 1. When bolting a magnesium alloy member using a galvanized washer, insulate the area between the galvanized washer and the magnesium alloy member so that the surrounding area of the galvanized washer does not come into direct contact with the magnesium alloy member. 1. A method for preventing electrolytic corrosion of a magnesium alloy member at a bolt assembly portion, the method comprising interposing a washer made of a flexible material.